Applications de l'interaction d'ondes élastiques à la mesure des propriétés non-linéaires des matériaux et à la caractérisation de champs de pression.

Abstract : This work presents a study of nonlinear elastic waves interaction, and different experimental techniques devoted to nonlinear properties measurement and high-pressure wave fields characterization. The study develops an analogy between fluids and solids within quadratic approximation, i.e. valid for longitudinal waves. The interaction of two longitudinal waves (30 and 2.5 MHz), equivalent to a phase modulation, allows to measure the nonlinearity coefficient of different kinds of materials, with samples thickness of order 10 mm. The results obtained in fluids, gels and solids, thanks to electronic improvement, shows the flexibility of this method. The specific elasticity of soft solids makes it possible to observe harmonic generation and interaction of shear waves, which are characteristic of the cubic nonlinearity and also confirms diffraction and near field effects. This latter are responsible for odd harmonics apparition. The 1D. transient elastography represents an experimental configuration which can be applied. An optical interferometer was used to measure high-pressure wave fields (at the focus of high-power transducers), and very small displacements (resulting from the radiation stress at the surface of a solid sample). The bandwidth broadening of optical setup and the improvement of phase detection methods make it possible to perform quantitative studies of nonlinear propagation phenomenon.
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Submitted on : Monday, September 5, 2005 - 8:00:00 AM
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Xavier Jacob. Applications de l'interaction d'ondes élastiques à la mesure des propriétés non-linéaires des matériaux et à la caractérisation de champs de pression.. Sciences de l'ingénieur [physics]. Université Paris-Diderot - Paris VII, 2005. Français. ⟨pastel-00001301⟩

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